Intellectual disability in cerebral palsy: a multifaceted
State Diagnostic and Counseling Center, K
This commentary is on the original article by Reid et al. on pages 687–
694 of this issue.
Reid et al.
describe the epidemiology of intellectual dis-
ability in cerebral palsy (CP) in terms of clinical and
neuroimaging associations, and report the impact of intel-
lectual disability on longevity and utilization of health ser-
vices. The study was undertaken in Melbourne, Australia
using three population-based CP cohorts from the Victo-
rian CP Register. Intellectual disability was deﬁned as a
tested IQ of less than 70 and was most often measured at
approximately 5 years of age.
CP was ﬁrst described during the mid-19th century and
since then clinicians have been aware of the multifaceted
nature of the condition. In 1889 Sir William Osler wrote,
‘More serious in many respects and more distressing to
friends and relations, are the mental defects so apt to be
associated with these cerebral palsies.’
Depending on the
CP subgroup, 25% to 80% of children have additional
impairments, such as intellectual disability, communication
difﬁculties, epilepsy, emotional disturbances, and visual
impairment. Although not always readily recognizable,
these deﬁcits can hamper the child’s ability to realize his
or her intrinsic developmental potential. Thus, cortical and
subcortical brain abnormality is likely to affect more than
just motor pathways. Despite this knowledge, the associ-
ated neurodevelopmental challenges of CP were not high-
lighted in its deﬁnition until recently.
Monitoring cognitive functioning in children with CP is
important and has implications for planning of educational
services and guiding interventions. The use of standard
measures of intelligence, however, frequently poses chal-
lenges and approximately one-third of children with CP
are unable to complete all tasks on such measures (due to
inadequate pointing and verbal ability, for instance). The
source of discrepancy in cognitive functioning between
individuals is complex and may depend on factors such as
timing of injury, aetiology, and extent and localization of
the cerebral lesion. Moreover, environmental stimulation
and social participation may modulate the quality of cogni-
In line with previous reports, the frequency of intellec-
tual disability was 45% in the CP population studied by
Reid et al.
and intellectual disability was associated with
non-ambulation, epilepsy, and grey matter injuries. The
authors often relied on clinical judgement when assessing
cognitive functioning and one of the limitations of the
study is the lack of comparisons across different levels of
intellectual disability. Children with CP frequently have
an uneven cognitive proﬁle with a higher Verbal than
Perceptual IQ. A correlation has been found between the
degree of impairment of non-verbal intelligence and the
amount of white matter reduction in optic radiations and
occipital lobes, suggesting that congenital damage to
these areas may selectively and persistently affect visu-
A subgroup of children with such
lesions may have cerebral visual impairment which indi-
cates difﬁculties with processing of visual information in
the presence of a (nearly) intact ophthalmological system.
Signs may be subtle, but the condition frequently has
impact on near vision tasks, letter recognition, and social
interaction, etc. For diagnostic purposes an ophthalmo-
logical assessment and screening for cerebral visual
impairment is indicated.
In the study by Reid et al.,
children with intellectual
disability had more hospital admissions classiﬁed as emer-
gency and multi-day, and longevity was comparatively
reduced for individuals with intellectual disability across all
Gross Motor Function Classiﬁcation System levels. In my
opinion, these ﬁndings are very important. Children with
CP and concomitant intellectual disability are a vulnerable
population. They frequently have difﬁculties expressing
themselves and communicating their feelings, pain, or
other symptoms of illnesses. Therefore, we as clinicians
need to emphasize preventive health measures and close
follow-up of children and adults with CP. In doing so we
can possibly limit hospital admissions and improve the
quality of life of these individuals.
1. Reid SM, Meehan EM, Arnup SJ, Reddihough DS. Intel-
lectual disability in cerebral palsy: a population-based ret-
rospective study. Dev Med Child Neurol 2018; 60: 687–94.
2. Osler W. The Cerebral Palsies of Children. London:
H.K. Lewis, 1889.
3. Rosenbaum P, Paneth N, Leviton A, et al. A report: the
deﬁnition and classiﬁcation of cerebral palsy April 2006.
Dev Med Child Neurol 2007; 49(Suppl. 109): 8–14.
4. Fazzi E, Bova S, Giovenzana A, Signorini S, Uggetti
C, Bianchi P. Cognitive visual dysfunctions in preterm
children with periventricular leukomalacia. Dev Med
Child Neurol 2009; 51: 974–81.
5. Ortibus E, Laenen A, Verhoeven J, et al. Screening for
cerebral visual impairment: value of a CVI questionnaire.
Neuropediatrics 2011; 42: 138–47.
640 Developmental Medicine & Child Neurology 2018, 60: 636–644